The present invention generally relates to an implantable cardiac stimulation system and more particularly to a universal pacing and defibrillation system capable of sensing cardiac activity, pacing, and defibrillating in all four chambers of the heart. The present invention is further directed to a lead implantable in the coronary sinus region of the heart which permits implementation of a universal pacing and defibrillation system with three leads.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Traditionally, therapy delivery had been limited to the venous, or right side of the heart. The reason for this is that implanted electrodes can cause blood clot formation in some patients. If a blood clot were released arterially from the heart left side, as for example the left ventricle, it could pass directly to the brain potentially resulting in a paralyzing or fatal stroke. However, a blood clot released from the right heart, as from the right ventricle, would pass into the lungs where the filtering action of the lungs would prevent a fatal or debilitating embolism in the brain.
Recently, new lead structures and methods have been proposed and even practiced for delivering cardiac rhythm management therapy to the left heart. These lead structures and methods avoid direct electrode placement within the left atrium and left ventricle of the heart by lead implantation within the coronary sinus region of the heart. As used herein, the phrase xe2x80x9ccoronary sinus regionxe2x80x9d refers to the venous vasculature of the left ventricle, including any portions of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus.
It has been demonstrated that electrodes placed in the coronary sinus region of the heart may be used for left atrial pacing, left ventricular pacing, or cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of a patient population with left ventricular dysfunction and/or congestive heart failure which would benefit from left heart side pacing, either alone or in conjunction with right heart side pacing (bi-chamber pacing), and/or defibrillation.
Cardiac leads intended for use in the left heart via the coronary sinus region are difficult to position due to the tortuous venous routes of the human anatomy. Moreover, to provide both pacing and defibrillation of both the left atrium and the left ventricle from the coronary sinus region with multiple leads employing the appropriate types of electrodes is extremely difficult given the space constrains to accommodate multiple leads in the coronary sinus region. Hence, such implants are too cumbersome, difficult, and time consuming to perform and would likely result in compromised performance or system malfunction.
Universal pacing and defibrillation systems, capable of pacing and defibrillating all four heart chambers of the heart would require numerous pacing and defibrillation electrodes to be employed within the heart and its coronary venous system. To implement such a universal pacing and defibrillation system utilizing current state of the art lead configuration approaches, an inordinate number of leads would be required. This would result in lengthy implant procedures and possibly more leads than the human anatomy is able to accommodate. An inordinate number of leads may also make it difficult to accurately locate each electrode at a most efficacious position within the heart.
Efforts to minimize the number of required leads could also be fraught with potential obstacles. Such an effort would most likely include loading a lead up with too many electrodes. While this would reduce the number of required leads, such a lead would be difficult to implant. More importantly, owing to the differences in physiology from one patient to another, such a lead would most likely not xe2x80x9cfitxe2x80x9d a large number of patients in terms of resulting efficacious electrode positioning.
Efforts to achieve a universal pacing and defibrillation system, if successful, could provide significant improved therapies. Coordinated right heart and left heart pacing therapies would be made possible. Further, improved defibrillation therapies would also be made possible. Such therapies could include improved defibrillation energy distribution within the heart and/or new and improved sequential defibrillation pulse techniques.
The present invention provides an implantable system for the defibrillation of the ventricles of a heart wherein a defibrillation pulse is delivered between first and second pluralities of electrodes, at least one of the electrodes being a left ventricular defibrillation electrode.
The implantable system includes a first lead configured for implant in the right ventricle of the heart and including a right ventricular defibrillation electrode, a second lead configured for implant in the right atrium of the heart, a right atrial defibrillation electrode carried by one of the first and second leads, and a third lead configured for implant in the coronary sinus region of the heart. The third lead includes a left ventricular defibrillation electrode and a left atrial defibrillation electrode, the left ventricular defibrillation electrode and the left atrial defibrillation electrode being spaced apart so that when the third lead is implanted in the coronary sinus region with the left ventricular defibrillation electrode adjacent the left ventricle, the left atrial defibrillation electrode is within the coronary sinus adjacent the left atrium.
The system further includes a power supply and a control circuit operatively associated with the power supply and the defibrillation electrodes and configured for delivering a ventricular defibrillation pulse between a first plurality of the defibrillation electrodes and a second plurality of the defibrillation electrodes. The second plurality of defibrillation electrodes includes the left ventricular defibrillation electrode.
In accordance with a further aspect of the present invention, the power supply and control circuit are contained within an electrically conductive cage which may serve as an additional electrode for delivering the defibrillation pulse.
The present invention further provides an implantable cardiac lead. The lead includes an elongated lead body, a first defibrillation electrode carried by the lead body, and an electrode assembly carried by the lead body proximal to the first defibrillation electrode, the electrode assembly including a second defibrillation electrode and at least the pacing electrode. The lead is configured for implant in the coronary sinus region of the heart and the first defibrillation electrode and the electrode assembly are spaced apart on the lead body so that when the lead is implanted in the coronary sinus region with the first defibrillation electrode adjacent the left ventricle, the second defibrillation electrode and the at least one pacing electrode of the electrode assembly are within the coronary sinus adjacent to and in electrical contact with the left atrium. The lead permits a system capable of defibrillating the ventricles from all four chambers of the heart to be implemented with three leads.